This application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2004-207459 filed in Japan on Jul. 14, 2004, Patent Application No. 2004-244136 filed in Japan on Aug. 24, 2004, Patent Application No. 2004-284795 filed in Japan on Sep. 29, 2004, and Patent application No. 2004-309846 filed in Japan on Oct. 25, 2004, the entire contents of which are hereby incorporated by reference.
The present invention relates to a development apparatus having a function to detect the remaining amount of a developer remaining in a development tank.
Development apparatuses need to be replaced with new ones when a developer is exhausted in a development tank. Therefore, the development apparatus is provided with a developer detecting mechanism for detecting the remaining amount of the developer held in the development tank.
As a technique relating to such a developer detecting mechanism, a developer detecting mechanism illustrated in FIG. 17 is known in the art (see, for example, JP 2004-12893A).
The developer detecting mechanism includes a toner stirring member 901 having a shape of substantially squared-C which transfers to a development roller (not shown) a developer (hereinafter referred to as a “toner”) held in a development tank (hereinafter referred to as a “toner tank”) 900, a rotating shaft 902 which supports the member 901 at an end thereof, and a gear 903 which rotates the rotating shaft 902 with external force.
Further, at the other end of the toner stirring member 901, a slit plate 905 which passes through a photosensor 904 is provided. The slit plate 905 is a disk having a plurality of slits. In the photosensor 904, a light emitting section and a light detecting section are disposed facing each other, and the slit plate 905 passes in between. Therefore, the light detecting section of the photosensor 904 is turned ON when a slit of the slit plate 905 passes through the photosensor 904 (receives light from the light emitting section).
In the toner tank 900, the substantially squared-C-shaped toner stirring member 901 is rotated to stir the toner and convey a portion of the toner to the development roller. When stirring, the toner stirring member 901 entering the toner (toner accumulation) held in the toner tank 900 receives resistance due to the toner, so that the rotational speed of the toner stirring member 901 is slowed at a moment. Therefore, the speed of the slit plate 905, which is rotated along with the toner stirring member 901 and passes through the photosensor 904, is slowed. Therefore, the cycle of light detection by the photosensor 904 (corresponding to a cycle in which the slit passes through the photosensor 904) is elongated.
On the other hand, when the toner stirring member 901 leaves the toner held in the toner tank 900, the resistance of the toner suddenly disappears, so that the rotational speed is increased at a moment. Therefore, the speed of the slit plate 905 passing through the photosensor 904 is similarly increased, so that the light detection cycle of the photosensor 904 is shortened.
A time from entering to leaving the toner of the toner stirring member 901 is decreased with a decrease in the amount of the toner held in the toner tank 900 (toner remaining amount). Therefore, the toner tank 900 estimates the toner remaining amount by monitoring a change in the light detection cycle of the photosensor 904.
In most printed images on recording paper, pixels are generally concentrated on a middle portion of the recording paper more than on an edge portion thereof. Therefore, the toner of the toner tank 900 is consumed in the middle portion thereof more than in both edge portions thereof, so that the toner level in the toner tank 900 becomes uneven as a whole, leading to occurrence of irregular density in printing.
However, in the above-described conventional developer detecting mechanism, the toner is only stirred in the toner tank 900 using the toner stirring member 901. Thus, the conventional developer detecting mechanism does not have an ability to convey the toner to a lateral direction. In other words, the conventional developer detecting mechanism does not have an ability to cause the toner level in the toner tank 900 to be uniform in an entire width direction of the toner tank 900. Therefore, when there occurs an extreme difference in the toner level between the middle portion and the edge portion of the toner tank 900, an error may occur in detection of the toner remaining amount and the detection accuracy may be insufficient.
Example embodiments of the are devised to solve the above-described problems. An object of an example embodiment is to provide a development apparatus having a high-detection-precision developer detecting mechanism which has both an ability to convey toner and an ability to stir the toner. Such a developer detecting mechanism is achieved by eccentrically distributing the gravity of developer by stirring and conveying toner to provide a function as a toner stirring member of the conventional technique.